Yes, absolutely right - double quotes. Replacing with single quotes makes '\W' work like a charm. Thanks.

But, just to be finicky and difficult, '\W\s' is still converting spaces to &#32.

UPDATE:

Ya, of course it was. This is the list of UNSAFE characters to be encoded. So if I include '\W\s', that specificlaly tells it to encode spaces. What I want is '^\w\s' - anything that's not a word char or a space. Works perfect now.

UPDATE 2

OK, now this is very cool. With this formulation, I can create a very well defined list of what is and is not to be encoded. For example (what I'm using):

$encoded = encode_entities($input'^\w\s.\-');
[download]

encodes everything that is NOT a word char, or a space, or a period, or a dash (backslash needed to escape 'cause the dash is part of the module's syntax)